Electron gun electrode supports



Jan. 16, 1962 E. F. SCHILLING ELECTRON GUN ELECTRODE SUPPORTS Filed Dec. 16, 1959 FIG.2.

INVENTORI EDMUND F LLING, 0W7

ilnited States Patent Ofifice 3,@l7,53l Patented Jan. 16, 1952 3,017,531 ELECTRON GUN ELECTRQDE SUPPQRTS Edmund F. Schilling, Dewitt, N.Y., assignor to General Electric Company, a corporation of New York Filed Dec. 16, 1959, Ser. No. 859,901 10 Claims. (Cl. 313-82) This invention relates to electron guns for cathode ray tubes and the like.

It is desirable in the operation of picture tubes for television and the like to utilize a luminescent screen potential which is as high as possible in order to obtain maximum screen brightness, minimum electron beam spot size, and optimum image sharpness. Conflicting with this aim of high screen potential is the requirement that the length of picture tube necks, and of the electron guns housed therein, be minimized, with attendant necessary reduction in spacing of the various electron gun electrodes. Since the final accelerating electrode of the electron gun of a television picture tube is usually operated at the same potential as the luminescent screen, deriving its potential for convenience from the common terminal on the envelope which supplies the screen potential, one resulting practical limitation on maximum screen potential in minimum neck length tubes has been the possibility of excessive leakage current or voltage breakdown between the final accelerating electrode of the electron gun and other lower voltage electrodes of the electron gun. Such voltage breakdown is of course highly objectionable and for all practical purposes renders the tube inoperative.

Accordingly, one object of the present invention is to provide an improved electron gun for television picture tubes and the like which can be operated at a higher electron gun final accelerating electrode potential, and hence a higher luminescent screen potential, than heretofore employed for television picture tubes without objectional voltage breakdown, and which electron gun has a minimum length particularly suitable for accommodation in short neck cathode ray tubes for television picture display and the like.

Another object is to provide an improved electron gun of the foregoing character which has improved mechanical strength and ruggedness.

These and other objects will be apparent from the following description together with the accompanying drawings, wherein;

FIGURE 1 is a fragmentary axial sectional view of a cathode ray tube having an electron gun constructed in accordance with the present invention;

FIGURE 2 is an enlarged view of the electron gun portion of the structure of FIGURE 1;

FIGURE 3 is a transverse sectional view of the structure of FIGURE 2 taken on the line 33 thereof;

FIGURE 4 is a view similar to FIGURE 2 showing a modified form of an electron gun constructed according to the present invention;

FIGURE 5 is a View similar to FIGURE 3 of another modified form of electron gun constructed according to the present invention.

Referring especially to FIGURES 1 and 2 of the drawing, there is shown a cathode ray tube including an envelope 2 having a faceplate portion 4 on the interior surface of which is deposited a luminescent screen 6, and having a neck portion 8 within which is mounted an electron gun 16 for generating an electron beam for exciting the screen. The electron gun 10 includes a control electrode 12 within which is mounted in indirectly heated cathode 14, a screen electrode 16, a first accelerating electrode 18, a focusing electrode 20, and a final accelerating electrode 22. All of these electrodes are of generally annular form having central apertures to pass the electron beam, and all are arranged in coaxially spaced relation along the common axis 24 which defines the path of the electron beam.

The final accelerating electrode 22 is maintained at a high voltage, of the order for example of 20 kv., and is conveniently supplied this high voltage from a terminal 26 in the envelope Wall through a conductive coating 28 on the interior surface of the envelope and resilient contact fingers 30 which also serve to support the forward or screenward end of the electron gun within the tube envelope. Suitable potentials for the cathode and its heater are supplied through a plurality of leads 32 extending through the closed end of the tube neck. The accelerating electrode 18 is desirably maintained at a high voltage at or near that of the final accelerating electrode 22, which voltage may be conveniently provided by a lead 34 extending from the final accelerating electrode 22 to electrode 18. Bi-potential focusing lens action is provided by maintaining the focus electrode 20 at a relatively low voltage, of the order for example of 300 to 500 volts, this potential being conveniently supplied by a lead 36 extending through the closed end of the tube neck. The potential of screen electrode 16, which likewise may be of the order of 300 to 500 volts, is also provided by a lead 38 extending through the neck closure.

In accordance with the invention the several electrodes are rigidly mechanically supported relative to one another by plural sets of supporting rods of insulating material such as glass, each set consisting of one or more rods, and the rod or rods of one set being secured only to the relatively low voltage electrodes such as those having the potential of the focus electrode 25 or screen electrode 16 and lower, and the high voltage electrodes such as accelerators 18 and 22 being connected only to the rod or rods of the other set.

As best shown in FIGURE 2, high voltage electrodes 18 and 22 are supported and maintained in fixed mutual relationship exclusively by a set of glass rods here shown as two in number 40, 42 which are spaced 180 apart about the axis 24 of the electron gun. The glass rods 40, 42 are connected to electrode 22 by a metal strap 44 Welded to the electrode and having its ends embedded in the glass rods. The rods 40, 42 are similarly connected to electrode 18 by a strap 46 and to the control electrode 12 by straps 4-3, 58. The low voltage elecrode 29 is likewise supported exclusively by diametrically spaced glass rods 54, 56 which are interspaced apart from the glass rods 40, 42. Electrode 2 0 is secured to rods 54, 56, by a metal strap 59 welded to the electrode and having its ends embedded in the rods, and the screen electrode 16 is similarly connected to the rods 54, 56 by means of a strap 60. Rods 54, 56 are also rigidly secured to the control electrode 12 by straps 62, 64 welded to the control electrodes and having their ends embedded in the rods.

With the arrangement described, it will be evident that the several electrodes 22, 18, 12 are supported in rigidly fixed properly spaced coaxial relation, and likewise electrodes 16 and 20 are rigidly supported in proper relative position to each other and to electrodes 22 and 18 by virtue of the common connection of rods 54, 56 and rods 40, 42 to the control grid 12. From the electrical standpoint, it will be evident that although the high voltage electrodes and low voltage electrodes can be spaced extremely closely in an axial direction for minimum overall electron gun length, nevertheless the only electrical leakage paths between high and low voltage electrodes are along the rods, and the structural supporting arrangement described insures maximum length to these electrical leakage paths between the high voltage electrodes and the low voltage electrodes. Thus the only electrical leakage path between electrode 2t and electrode 22 is a leakage path which includes substantially the entire length of rods 54, 56 plus a substantial portion of rods 4% 42, a total distance many times that which would exist between electrodes 22 and 2% if both were supported by the same set of support rods. Similarly the electrical leakage path between electrode 18 and electrode 2% involves substantially half of the length of rods 46, 42 and the length of the rods 54, 56, a total distance substantially in excess of that which would exist between electrodes 18 and 20 if both were supported by the same set of support rods. Moreover it will be apparent that with the arrangements shown there are only two leakage paths between any high voltage electrode and any low voltage electrode.

An additional feature of a modified form of the present invention is shown in FIGURE 4 wherein an extension of one of the glass rods 56 supporting the low voltage electrode 20 is secured to the annular radially extending flange of the high voltage electrode 22. Alternatively rod 56 may be secured to the cylindrical portion of electrode 22 by a strap spaced as far from strap 59 as possible. While this connection of rod 56 to electrode 22 adds an additional leakage path along the extended por tion of the rod 56 between the high voltage electrode 22 and the low voltage electrode 20, it has the advantage of affording enhanced rigidity to the electron gun by a common connection of the two sets of rods both at the control grid 12 at the rearward end of the gun and at the high voltage electrode 22 at the forward end of the gun.

FIGURE 8 shows another arrangement of the glass rods 40, 42 and 54, 56 in which adjacent rods of alternate sets are spaced apart less than 90, and preferably approximately 60, in order to facilitate jigging or mandrel supporting of the parts during assembly of the electron gun.

It will be appreciated by those skilled in the art that the invention may be carried out in various ways and may take various forms and embodiments other than those illustrative embodiments heretofore described. It is to be understood that the scope of the invention is not limited by the details of the foregoing description, but will be defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electron gun having a cathode for emitting electrons and electron beam forming means including a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode, said electrodes including at least one accelerating electrode adapted to be maintained at a predetermined first voltage level and at least one focus electrode next adjacent said one accelerating electrode adapted to be maintained at a voltage level substantially different from said first voltage level, first and second sets of insulating support means for supporting said electrodes, means connecting said accelerating electrode to one only of said sets of insulating support means, and means connecting said focus electrode to the other only of said sets of insulating support means.

2. In an electron gun having a cathode for emitting electrons and electron beam forming means including a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode, said electrodes having openings through which said electron beam path extends, said electrodes including at least one high voltage electrode and at least one low voltage electrode, first and second sets of insulating electrode support rods extending generally parallel to said electron beam path,

each of said sets of insulating support rods extending .along said electron beam path from opposite said one high voltage electrode to opposite said one low voltage electrode, means connecting said high voltage electrode to said first set only of said insulating support rods, and means connecting said low voltage electrode to said second set only of said insulating support rods.

3. In an electron gun having a cathode for emitting electrons and electron beam forming means including a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode, said electrodes including at least one accelerating electrode adapted to be maintained at a predetermined first voltage level and at least one focus electrode adjacent to said accelerating electrode adapted to be maintained at a volt age level substantially different from said first voltage level, first and second sets of insulating support rods for supporting said electrodes, first respective strap means secured to said accelerating electrode and embedded in the insulating support rods of only said first set, and additional respective strap means secured to said focus electrode and embedded in the insulating support rods of only said second set. V

4. In an electron gun having a cathode for emitting electrons and a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode and having openings through which said electron beam path extends, said electrodes including a final accelerating electrode adapted to be maintained at a relatively high voltage, a focus electrode between the final accelerating electrode and cathode and adapted to be maintained at a relatively low voltage, and a control electrodebetween the focus electrode and cathode, first insulating support means, means connecting said final accelerating electrode to said first only of said insulating support means, second insulating support means spaced from said first insulating support means, and means connecting said focus electrode to said second only of said insulating support means.

5. In an electron gun having a cathode for emitting electrons and electron beam forming means including a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode, said electrodes having openings through which said electron beam path extends, said electrodes including at least one accelerating electrode adapted to be maintained at a relatively high voltage, a focus electrode adapted to be maintained at a relatively low voltage, and a control electrode between the focus electrode and cathode and adapted to be maintained at a relatively low voltage, first and second sets of insulating electrode support rods extending generally parallel to said electron beam path, means connecting said accelerating electrode to said first set of said insulating support rods, means connecting said focus electrode to said second set only of said insulating support rods, and at least one rod of said second set being supportingly engaged with said accelerating electrode.

6. In an electron gun having a cathode for emitting electrons and electron beam forming means including a plurality of electrodes spaced along a predetermined electron beam path extending from said cathode, said electrodes having openings through which said electron beam path extends, said electrodes including at least one accelerating electrode adapted to he maintained at a rela tively high voltage, a focus electrode adapted to be maintained at a relatively low voltage, and a control electrode between the focus electrode and cathode and adapted to be maintained at a relatively low voltage, a first set of insulating support rods connected to and supporting said accelerating electrode and control grid, and a second set of insulating support rods connected to and supporting said focus electrode and control grid.

7. An electron gun comprising a cathode for emitting electrons along a predetermined electron beam path, electron beam forrning means including a plurality of electrodes through which said path extends, said electrodes including in order along said path a control electrode, a screen electrode, a first accelerating electrode, a focus electrode and a final accelerating electrode, said accelerating electrodes being adapted to be maintained at a relatively high voltage and said focus and screen and control electrodes being adapted to be maintained at a relatively low voltage, first and second sets of insulating electrode support rods extending generally parallel to said path, means connecting said accelerating electrodes to said first set only of said support rods, and means connecting said focus electrode to said second set only of said support rods.

8. An electron gun comprising a cathode for emitting electrons along a predetermined electron beam path, electron beam forming means including a plurality of electrodes through which said path extends, said electrodes including in order along said path a control electrode, a screen electrode, a first accelerating electrode, a focus electrode and a final accelerating electrode, said accelerating electrodes being adapted to be maintained at a relatively high voltage and said focus and screen and control electrodes being adapted to be maintained at a relatively low voltage, first and second sets of insulating electrode support rods extending generally parallel to said path, first respective strap means secured to said control electrode and first accelerating electrode and final accelerating electrode and being embedded in the insulating rods of only said first set, additional respective strap means secured to said control electrode, screen electrode and focus electrode and being embedded in the rods of only said second set.

9. An electron gun as defined in claim 8 wherein the first set of rods comprises two rods diametrically spaced of said first set.

10. An electron gun comprising a cathode for emitting electrons along a predetermined electron beam path, electron beam forming means including a plurality of electrodes through which said path extends, said electrodes including in order along said path a control electrode, a screen electrode, a first accelerating electrode, a focus electrode and a final accelerating electrode, said accelerating electrodes being adapted to be maintained at a relatively high voltage and said focus screen and control electrodes being adapted to be maintained at a relatively low voltage, first and second sets of insulating electrode support rods extending generally parallel to said path, first respective strap means secured to said control electrode and first accelerating electrode and final accelerating electrode and being embedded in the insulating rods of only said first set, additional respective strap means secured to said control electrode, screen electrode and focus electrode and being embedded in the rods only of said second set, and at least one rod of said second set having an extended portion secured to said final accelerating electrode.

References Cited in the file of this patent UNITED STATES PATENTS 2,732,511 Dichter Jan. 24, 1956 2,778,966 Faustini Jan. 22, 1957 2,840,739 Lesovicz June 24, 1958 2,853,639 Knochcl Sept. 23, 1958 2,909,689 Case Oct. 20, 1959 

